OSX/utilities/der_number.c

   1 /*
   2  * Copyright (c) 2012,2014 Apple Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24
  25
  26 #include <stdio.h>
  27
  28 #include "utilities/SecCFRelease.h"
  29 #include "utilities/der_plist.h"
  30 #include "utilities/der_plist_internal.h"
  31
  32 #include <corecrypto/ccder.h>
  33 #include <CoreFoundation/CoreFoundation.h>
  34
  35
  36 const uint8_t* der_decode_number(CFAllocatorRef allocator, CFOptionFlags mutability,
  37                                  CFNumberRef* number, CFErrorRef *error,
  38                                  const uint8_t* der, const uint8_t *der_end)
  39 {
  40     if (NULL == der)
  41         return NULL;
  42
  43     size_t payload_size = 0;
  44     const uint8_t *payload = ccder_decode_tl(CCDER_INTEGER, &payload_size, der, der_end);
  45
  46     if (NULL == payload || (ssize_t) (der_end - payload) < (ssize_t) payload_size) {
  47         SecCFDERCreateError(kSecDERErrorUnknownEncoding, CFSTR("Unknown number encoding"), NULL, error);
  48         return NULL;
  49     }
  50     if (payload_size > sizeof(long long)) {
  51         SecCFDERCreateError(kSecDERErrorUnsupportedNumberType, CFSTR("Number too large"), NULL, error);
  52         return NULL;
  53
  54     }
  55
  56     long long value = 0;
  57
  58     if (payload_size > 0) {
  59         if ((*payload & 0x80) == 0x80)
  60             value = -1; // Negative integers fill with 1s so we end up negative.
  61
  62         const uint8_t* const payload_end = payload + payload_size;
  63
  64         for (const uint8_t *payload_byte = payload;
  65              payload_byte < payload_end;
  66              ++payload_byte) {
  67             value <<= 8;
  68             value |= *payload_byte;
  69         }
  70     }
  71
  72     *number = CFNumberCreate(allocator, kCFNumberLongLongType, &value);
  73
  74     if (*number == NULL) {
  75         SecCFDERCreateError(kSecDERErrorAllocationFailure, CFSTR("Number allocation failed"), NULL, error);
  76         return NULL;
  77     }
  78
  79     return payload + payload_size;
  80 }
  81
  82
  83 static inline uint8_t byte_of(size_t byteNumber, long long value)
  84 {
  85     return value >> (8 * (byteNumber - 1));
  86 }
  87
  88 static inline size_t bytes_when_encoded(long long value)
  89 {
  90     size_t bytes_encoded = sizeof(long long);
  91
  92     uint8_t first_byte = byte_of(bytes_encoded, value);
  93
  94     // Skip initial 0xFFs or 0x00
  95     if (first_byte == 0xFF || first_byte == 0x00) {
  96         do {
  97             --bytes_encoded;
  98         } while (bytes_encoded > 1 && (byte_of(bytes_encoded, value) == first_byte));
  99
 100         if ((first_byte & 0x80) != (byte_of(bytes_encoded, value) & 0x80))
 101             bytes_encoded += 1;
 102     }
 103
 104     return bytes_encoded;
 105 }
 106
 107 size_t der_sizeof_number(CFNumberRef data, CFErrorRef *error)
 108 {
 109     long long value;
 110     if (!CFNumberGetValue(data, kCFNumberLongLongType, &value))
 111         return 0;
 112
 113     return ccder_sizeof(CCDER_INTEGER, bytes_when_encoded(value));
 114 }
 115
 116 uint8_t* der_encode_number(CFNumberRef number, CFErrorRef *error,
 117                            const uint8_t *der, uint8_t *der_end)
 118 {
 119     long long value;
 120     if (!CFNumberGetValue(number, kCFNumberLongLongType, &value))
 121         return NULL;
 122
 123     size_t first_byte_to_include = bytes_when_encoded(value);
 124
 125     if (!der_end || (ssize_t) (der_end - der) < (ssize_t) first_byte_to_include)
 126         return NULL;
 127
 128     // Put the bytes we should include on the end.
 129     for(size_t bytes_included = 0; bytes_included < first_byte_to_include; ++bytes_included)
 130     {
 131         --der_end;
 132         *der_end = value & 0xFF;
 133         value >>= 8;
 134     }
 135
 136     return ccder_encode_tl(CCDER_INTEGER, first_byte_to_include, der, der_end);
 137
 138 }